Stationary induction electric apparatuses such as a transformer and a reactor are used in a middle of a system transmitting electricity from a power plant to customers such as factories, buildings, and houses. In the stationary induction electric apparatus, a stationary induction electric apparatus main body (the main bodies of the transformer, the reactor, and so on) is insulated by using, for example, a liquid insulating medium (insulating oil and so on). Here, it is general that a bushing is used for a connection of the stationary induction electric apparatus and an air wiring (a power transmission line and so on). For example, electric power from the power transmission line is introduced into the stationary induction electric apparatus main body via an air bushing at outside of the stationary induction electric apparatus and an oil bushing at inside of the stationary induction electric apparatus.
There is a case when the stationary induction electric apparatus is connected to a gas-insulated apparatus such as a GIS (Gas Insulated Switch). In this case, the liquid insulating medium at the stationary induction electric apparatus side and an air insulating medium at the gas-insulated apparatus side are divided by using a spacer instead of the air bushing.